Curable resin systems containing cyanate ester functional oxazolinylpolysiloxanes

Abstract

Cyanate-functional oxazolinylpolysiloxanes are useful for toughening high performance resin systems such as cyanates, epoxies, and bismaleimides without substantial loss of heat resistance.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows: 
     
       1. A cyanate-functional oxazolinylpolysiloxane modifier for heat curable resins which comprises the reaction product of an epoxy-functional polysiloxane and a polycyanate-functional monomer. 
     
     
       2. The modifier of claim 1 wherein said epoxy functional polysiloxane is a bis[3-glycidoxypropyl]polysiloxane. 
     
     
       3. The modifier of claim 1 wherein the mole ratio of cyanate groups in the polycyanate functional monomer to epoxy groups in the epoxy-functional polysiloxane is at least 2:1. 
     
     
       4. The modifier of claim 2 wherein the mole ratio of cyanate groups in the polycyanate functional monomer to epoxy groups in the epoxy-functional polysiloxane is at least 2:1. 
     
     
       5. The modifier of claim 2 wherein said epoxyfunctional polysiloxane corresponds to the formula: ##STR2## wherein each R is individually selected from the group consisting of C 1  -C 6  lower alkyl, C 1  -C 6  lower alkoxy, C 1-C   6  haloalkyl, vinyl, allyl, allyloxy, propenyl, propenyloxy, acetoxy, C 5  -C 10  cycloalkyl, and aryl radicals and wherein n is an integer from 1 to about 10,000. 
     
     
       6. The modifier of claim 5 wherein each R is individually selected from the group consisting of methyl and phenyl radicals. 
     
     
       7. The modifier of claim 1 wherein said polycyanate-functional monomer is a dicyanate. 
     
     
       8. The modifier of claim 7 wherein said dicyanate is selected from the group consisting of the cyanates of hydroquinone, bisphenol A, bisphenol F, bisphenol S, 2,2',6,6'-tetramethylbisphenol F, and phenolated dicyclopentadiene. 
     
     
       9. The modifier of claim 2 wherein said polycyanate-functional monomer is a dicyanate. 
     
     
       10. The modifier of claim 9 wherein said dicyanate is selected from the group consisting of the cyanates of hydroquinone, bisphenol A, bisphenol F, bisphenol S, 2,2',6,6'-tetramethylbisphenol F, and phenolated dicyclopentadiene. 
     
     
       11. A process for toughening a heat-curable resin comprising adding thereto a toughening amount of the cyanate-functional oxazolinylpolysiloxane of claim 1. 
     
     
       12. The process of claim 11 wherein said heat-curable resin is selected from the group consisting of cyanate-functional resins, epoxy resins, bismaleimide resins, and mixtures thereof, wherein the term cyanate-functional resin excludes the cyanate-functional oxazolinylpolysiloxanes. 
     
     
       13. A polysiloxane elastomer of the cyanate-functional oxazolinylpolysiloxane of claim 1.